Add Mailgun base_url sender config option

CHANGELOG.md

@@ -6,6 +6,7 @@
 - Added new Gmail user agent to avoid tracking invalid clicks/opens
 - Return to list of unsubscribed/unreachable contacts after delete action from
   one of those pages. Implements #193 (thanks @digitalfredy for reporting)
+- It's now possible to choose between the US and EU API endpoints for Mailgun senders (thanks @harryfear for reporting)
 
 ## Fixed
 - Clicking "Delete all" on the contacts list no longer causes a server error

lib/keila/mailings/sender_adapters/mailgun.ex

@@ -4,18 +4,21 @@ defmodule Keila.Mailings.SenderAdapters.Mailgun do
   @impl true
   def name, do: "mailgun"
 
+  @base_url "https://api.mailgun.net/v3"
+
   @impl true
   def schema_fields do
     [
       mailgun_api_key: :string,
-      mailgun_domain: :string
+      mailgun_domain: :string,
+      mailgun_base_url: :string
     ]
   end
 
   @impl true
   def changeset(changeset, params) do
     changeset
-    |> cast(params, [:mailgun_api_key, :mailgun_domain])
+    |> cast(params, [:mailgun_api_key, :mailgun_domain, :mailgun_base_url])
     |> validate_required([:mailgun_api_key, :mailgun_domain])
   end
 
@@ -24,7 +27,8 @@ defmodule Keila.Mailings.SenderAdapters.Mailgun do
     [
       adapter: Swoosh.Adapters.Mailgun,
       api_key: config.mailgun_api_key,
-      domain: config.mailgun_domain
+      domain: config.mailgun_domain,
+      base_url: config.mailgun_base_url || @base_url
     ]
   end
 end

lib/keila_web/templates/sender/_mailgun_config.html.heex

@@ -5,6 +5,21 @@
   <% end %>
 </div>
 
+<div class="form-row">
+  <%= label(@form, :mailgun_base_url, "Base URL") %>
+  <%= with_validation(@form, :mailgun_base_url) do %>
+    <%= select(
+      @form,
+      :mailgun_base_url,
+      [
+        "https://api.mailgun.net/v3",
+        "https://api.eu.mailgun.net/v3"
+      ],
+      class: "text-black"
+    ) %>
+  <% end %>
+</div>
+
 <%= if is_nil(input_value(@form, :mailgun_api_key)) do %>
   <div class="form-row">
     <%= label(@form, :mailgun_api_key, gettext("API Key")) %>